1. Field
Curable compositions, such as oxazine-based ones, are useful in applications within the aerospace industry, such as for example as a thermosetting resin composition for use as a matrix resin in processes, such as resin transfer molding, vacuum assisted transfer molding, resin film infusion, prepregging and towpregging, where the composites or laminates so prepared have superior surface finish and high fiber consolidation.
2. Brief Description of Related Technology
Epoxy resins with various hardeners have been used extensively in the aerospace industry, both as adhesives and as matrix resins for use in prepreg assembly with a variety of substrates.
Blends of epoxy resins with other resins are known. See e.g. U.S. Pat. No. 4,607,091 (Schreiber), U.S. Pat. No. 5,021,484 (Schreiber), U.S. Pat. No. 5,200,452 (Schreiber), and U.S. Pat. No. 5,445,911 (Schreiber). These blends appear to be potentially useful in the electronics industry as the epoxy resins can reduce the melt viscosity of oxazines allowing for the use of higher filler loading while maintaining a processable viscosity. However, epoxy resins oftentimes undesirably increase the temperature at which oxazines polymerize.
Ternary blends of epoxy resins are also known. See U.S. Pat. No. 6,207,786 (Ishida), and S. Rimdusit and H. Ishida, “Development of new class of electronic packaging materials based on ternary system of benzoxazine, epoxy, and phenolic resin,” Polymer, 41, 7941-49 (2000).
Resin transfer molding (“RTM”) is a process by which a resin—conventionally and predominately, epoxy-based resin systems and maleimide-based systems—is pumped at low viscosities and under pressure into a closed mold die set containing a preform of dry fabric. The resin infuses into the preform to make a fiber-reinforced composite article. The RTM process can be used to produce at low cost composite parts that are complex in shape. These parts typically require continuous fiber reinforcement along with inside mold line and outside mold line controlled surfaces.
Fiber-reinforced composite articles may be manufactured from vacuum assisted resin transfer molding (“VaRTM”), like RTM but with an applied vacuum. VaRTM typically employs an open mold and places the system under a vacuum to assist the resin infusion process.
Resin film infusion (“RFI”), like RTM, infuses a resin into a preform placed in a mold. Here, however, the resin is in the form of a film, which is placed in the mold together with the preform. U.S. Pat. No. 5,902,535 speaks to RFI molds and processes, and is expressly incorporated herein by reference.
The matrix resin used in the RTM and VaRTM advanced possesses a low injection viscosity to allow complete wetting and infusion of the preform.
U.S. Patent Application Publication No. 2007/0007692 refers to resin transfer molding, vacuum assisted resin transfer molding and resin film infusion processes, using a heat curable composition having a benzoxazine component.
Notwithstanding the state of the technology, there is a need for new resin systems for advanced processes, particularly a resin system with improved performance properties.